A Quantitative study of alkyl radical reactions by kinetic spectroscopy. Part I. Mutual combination of methyl radicals and combination of methyl radicals with nitric oxide

Abstract

Combination reactions of the methyl radical have been studied by following the decay of the absorbance of the methyl radical during the course of the reaction by means of kinetic spectroscopy. The limiting values of the second-order rate constants at high pressure were determined for two reactions at room temperature:k, = (2.6 f 0.3) x 1O1O 1 mole-1 sec-1 CH, + N O ( + M ) .+ CH,NO ( + M ) :The extinction coefficient of the methyl radical was found to have a maximum value of (1.02 f 0.06) x lo4 1 mole-l cm-l at 216.4 nm. Integration of the extinction coefficient over the absorption band of the methyl radical gave an oscillator strength of 1.0 x

The reactions of methyl radicals with atomic and molecular oxygen

“…Since both of these studies measured relative rates, with literature values for both reference rate constants varying by a factor of 2, this disagreement is not surprising. There are now conflicting results reported for three different reactions (CH, + CH, [29,30], 0 + CH, [5 and present results], and CH, + O2 a t high pressures [14-161) that need to be resolved in order to form a consistent set of rate constants for the methyl radical.…”

The flash photolysis of azomethane. Minor products from the photolysis of methyl radicals and a rate constant for CH3 + NO

“…Both Van den Bergh and Callear [6] and Basco and coworkers [3] experienced difficulty in measuring k z because, in order to obtain a significant enhancement of the rate of CHa decay, they had to work very close to the limit of the time resolution of their apparatus. Even after correcting the limiting high-pressure value of Basco and coworkers factor of 2.5 still remains between the two determinations.…”

Sensitivity and correlation analysis of the physical parameters in absorption, four‐wave mixing, and Schlieren experiments

“…Since the methyl radical has a large cross section [24,25] for optical absorption near 216 nm, absorption studies have been performed by a number of groups to measure formation rates from various sources and the rate of methyl-methyl recombination [26-351. The most important process below 1800 K at pressures near 1 Atm is recombination to form ethane.…”